S-n-butyl-N,N-diisopropyl thiocarbamate as a selective herbicide in sugarbeets, carrots and cabbage

ABSTRACT

S-n-butyl-N,N-diisopropyl thiocarbamate which has the structural formula   &lt;IMAGE&gt;   which is useful as a selective herbicide in sugarbeets, carrots and cabbage.

BACKGROUND OF THE INVENTION

An herbicide is a compound which controls or modifies plant growth, e.g.killing, retarding, defoliating, desiccating, regulating, stunting,tillering, stimulating, and dwarfing. "Plants" refer to all physicalparts, including seeds, seedlings, saplings, roots, tubers, stems,stalks, foliage, and fruits. "Plant growth" is meant to include allphases of development from seed germination to natural or inducedcessation of life.

Herbicides are generally used to control or eradicate weed pests. Theyhave gained a high degree of commercial success because it has beenshown that such control can increase crop yield and reduce harvestingcosts.

Herbicidal effectiveness is dependent upon several variables. One ofthese is the time or growth related method of application. In the past,the most popular methods of application included: pre-plantincorporation into the soil, pre-emergence surface treatment of seededsoil, and post-emergence treatment of the plant and soil.

The most important determinant of herbicidal effectiveness is thesusceptibility of the target weed. Certain herbicidal compounds arephytotoxic to some weed species but not to others.

The manufacturer of the herbicide recommends a range of rates andconcentrations calculated to maximize weed control. The range of ratesvaries from approximately 0.01 to 50 pounds per acre (0.0112 to 56kilograms per hectare (k/ha)), usually from 0.1 to 25 pounds per acre(0.112 to 28 k/ha). The actual amount used depends upon severalconsiderations, including particular weed susceptibility and overallcost limitations.

Thiocarbamate herbicides are known to be particularly effective in thecontrol of grassy type weeds which interfere with the cultivation of awide variety of crops, e.g., barley, corn, lentils, peanuts, peas,potatoes, soybeans, spinach, tobacco, sugarbeets, carrots, cabbage andtomatoes.

Unfortunately, the thiocarbamates, like many other herbicides, are notselective exclusively off weed species. Many are toxic to both weeds andthe intended crop beneficiary. Therefore, a particular herbicide's usemay be proscribed by its injurious effect on the cultivated crop eventhough it may otherwise provide excellent control of weeds plaguing thatcrop.

SUMMARY OF THE INVENTION

The present invention pertains to the discovery that theS-n-butyl-N,N-diisopropyl thiocarbamate has the remarkable effect ofcontrolling nutsedge, watergrass and other weeds when applied at certainrates in a pre-emergence manner, while at the same rate exhibitingessentially no adverse effect to sugarbeets, carrots and cabbage.

The selectivity toward sugarbeets, carrots and cabbage that is possessedby the compound of this invention is quite unexpected and surprising inlight of the fact that homologous compounds are not nearly as effective.

DESCRIPTION OF THE INVENTION

This invention is directed to the use of S-n-butyl-N,N-diisopropylthiocarbamate as a selective herbicide for use on sugarbeets, carrotsand cabbage crops. Sugarbeets, carrots and cabbage show a high degree oftolerance to S-n-butyl-N,N-diisopropyl thiocarbamate.

The above herbicidal compound and those to which it is compared can beprepared by the general methods described inThiolcarbamates--Preparation and Molar Refractions, American ChemicalSociety, 81, 714 (1959). The thiocarbamate compounds are knownherbicides and their method of synthesis is well known. See U.S. Pat.Nos. 2,913,327, 2,983,747, 3,133,927, 3,175,897, and 3,185,720, forexample. However, in general the thiocarbamates produce unacceptableinjury to sugarbeets, carrots and cabbage. Therefore, it is quiteunexpected to discover the high degree degree of tolerance exhibitedtoward S-n-butyl-N,N-diisopropyl thiocarbamate.

It has been discovered that S-n-butyl-N,N-diisopropyl thiocarbamate isparticularly effective in control of nutsedge and other weeds. This isparticularly unexpected in that extremely close prior art homologs showno such superior control.

The compound of the present invention can be prepared according to theteaching of the following example.

EXAMPLE S-n-Butyl-N,N-diisopropyl thiocarbamate ##STR2##

A sodium dispersion in xylene was prepared by blending 75 grams (g) offinely divided sodium into 300 g (345 cubic centimeters (cc)) ofanhydrous xylene. The experimental equipment was an argon-flushed 1liter, 4-neck flask provided with a truebone stirrer, constant pressuredropping funnel air condenser and thermometer.

Anhydrous xylene (100 cc) and 18.2 cc (0.119 mole) of the sodiumdispersion was added to the reaction flask producing a purplishhueddispersion. n-Butyl mercaptan (13.4 g, 0.149 mole) dissolved in 25 cc ofxylene was added to the flask over a period of 4.5 minutes while thetemperature of reaction mixture rose from 35° C. to 76° C. The reactionmixture was heated to reflux and 19.5 g (0.119 mole) ofdiisopropylcarbamyl chloride was reacted with the reaction mixture over7.5 minutes. The resultant reaction mixture was then heated at refluxfor 1.5 hours, cooled and allowed to stand for 2 days. The mixture wasthen filtered through super-cell. The filter cake was washed with 25 ccof toluene and the filtrate combined and evaporated on a steam bath toproduce 25.4 g of a liquid. The fraction from 142° C. to 143.5° C. wasrecovered as product. The product was 17.72 g of a liquid having ann_(D) ³⁰ of 1.4753. Yield was 68.6% of theoretical of the titlecompound. The structure was confirmed by infrared spectrascopy. Thiscompound will be referred to as Compound No. 1.

Compound No. 1 was comparatively tested with other thiocarbamateherbicides for selectively controlling watergrass [Echnichloa crusgalli(L.) Beauv.], foxtail (Seteria sp.), Johnsongrass (Sorghum halepense),wild cane (Sorghum bicolor), and nutsedge (Cyperus spp.) by pre-emergentapplication on these weeds and sugarbeets, carrots and cabbage.

The additional herbicides tested are S-tert-butyl N,N-dipropylthiocarbamate, described in U.S. Pat. No. 2,913,327 (Compound No. 2) andS-n-propyl N,N-di-n-butyl thiocarbamate, described in U.S. Pat. No.2,913,327 (Compound No. 3).

Pre-Emergence Herbicide Screening Test

A mini field test carried out in which Compounds 1, 2, and 3 werepre-plant incorporated (PPI) at 6 lb/A approximately 3 inches deep in aloam soil and two rows of yellow nutsedge tubers were planted 1 inchapart and 1.5 inches deep through the plots which werew 11 feet long and4 feet wide. Compound No. 1 was also applied PPI at 3 lb/A. Each plotalso contained four rows of cotton planted 1.5 inch deep and rows ofyellow foxtail, watergrass, johnsongrass, wild cane, sugarbeets, cabbageand carrots, planted 0.5 inch deep. The results taken 3 weeks aftertreatment are shown in Table I.

The percent control of the weeds is based on the total injury to theplants due to all factors of injury. The rating system is from 0 to 100percent, where the value represents percent control. For example, 0represents no herbicidal effect with growth equal to untreated controlsand 100 represents complete control. The results are reported in TableI.

                                      TABLE I                                     __________________________________________________________________________            % Injury or Control 21 Days After Treatment                           Comp.                                                                             Rate                                                                              Nut-                                                                             Yellow                                                                            Water-                                                                            Johnson                                                                            Wild                                                                             Sugar                                              No. (lb/A)                                                                            grass                                                                            foxtail                                                                           grass                                                                             grass                                                                              cane                                                                             beets                                                                             carrots                                                                           cabbage                                    __________________________________________________________________________    1   3   58 70  90  60   35 0    0   0                                             6   100                                                                              90  97  85   40 0   10   0                                         2   6   40 90  94  95   90 0    0  100                                        3   6   50 80  70  90   94 90  30  90                                         __________________________________________________________________________

The compound of the present invention is useful as an herbicide,especially as a pre-emergence herbicide, and can be applied in a varietyof ways at various concentrations. The compound is applied to the soilwhere control of undesirable vegetation is desired. Preferably, thepre-emergence application is made a day or two before planting of thesugarbeets, carrots, cabbage or crop, on the data of planting or a dayor two after planting of the sugarbeets, carrots or cabbage.

In the preferred practice, the compound herein defined is formulatd intoherbicidal compositions, by admixture, in herbicidally effectiveamounts, with the adjuvants and carriers normally employed forfacilitating the dispersion of active ingredients for agriculturalapplications, recognizing the fact that the formulation and mode ofapplication of a toxicant may affect the activity of the material in agiven application. Thus, the active herbicidal compound may beformulated as granules of relatively large particle size, as wettablepowders, as emulsifiable concentrates, as powdery dusts, as solutions oras any of several other known types of formulations, depending upon thedesired mode of application.

Preferred formulations of pre-emergence herbicidal applications arewettable powders, emulsifiable concewntrates and granules. Theseformulations may contain as little as about 0.5% to as much as about 95%or more by weight of active ingredient.

Crop injury and herbicidal effectiveness depends upon several factors,including the nature of the soil where control is desired and the typesof seeds or plants to be controlled. Therefore, the rate of whichdispersion readily in water or other dispersants. The wettable powder isultimately applied to the soil either as a dry dust or as a dispersionin water or other liquid. Typical carriers for wettable powders includefuller's earth, kaolin clays, silicas and other readily wet organic orinorganic diluents. Wettable powders normally are prepared to containabout 5% to about 95% of the active ingredient and usually also containa small amount of wetting, dispersing, or emulsifying agent tofacilitate wetting and dispersion.

Emulsifiable concentrates are homogeneous liquid compositions which aredispersible in water or other dispersant, and may consist entirely ofthe active compound with a liquid or solid emulsifying agent, or mayalso contain a liquid carrier, such as xylene, heavy aromatic naphthas,isophorone and other non-volatile organic solvents. For herbicidalapplication, these concentrates are dispersed in water or other liquidcarrier and normally applied as a spray to the area to be treated. Thepercentage by weight of the essential active ingredient may varyaccording to the manner in which the composition is to be applied, butin general comprises about 0.5% to 95% of active ingredient by weight ofthe herbicidal composition.

Granular formulations wherein the toxicant is carried on relativelycoarse particles, are usually applied without dilution to the area inwhih suppression of vegetation is desired. Typical carriers for granularformulations include sand, fuller's earth, bentonite clays, vermiculite,perlite and other organic or inorganic materials which absorb or whichmay be coated with the toxicant. Granular formulations normally areprepared to contain about 5% to about 25% of active ingredients whichmay include surface-active agents such as heavy aromatic naphthas,kerosene or other petroleum fractions, or vegetable oils; and/orstickers such as destrins, glue or synthetic resins.

Typical wetting, dispersing or emulsifying agents used in agriculturalformulations include, for example, the alkyl and alkylaryl sulfonatesand sulfates and their sodium salts; polyhydric alcohols; and othertypes of surface-active agents, many of which are available in commerce.The surface-active agent, when used, normally comprises from 0.1% to 15%by weight of the herbicidal composition.

Dusts, which are free-flowing admixtures of the active ingredients withfinely divided solids such as talc, clays, flours and other organic andinorganic solids which act as dispersants and carriers for the toxicant,are useful formulations for soil-incorporating application.

Pastes, which are homogeneous suspensions of a finely divided solidtoxicant in a liquid carrier such as water or oil, are employed forspecific purposes. These formulations normally contain about 5% to about95% of active ingredient by weight, and may also contain small amountsof a wetting, dispersing or emulsifying agent to facilitate dispersion.For application, the pastes are normaly diluted and applied as a sprayto the area to be affected.

Other useful formulations for herbicidal applications include simplesolutions of the active ingredient in a dispersant in which it iscompletely soluble at the desired concentration, such as acetone,alkylated naphthalenes, xylene and other organic solvents. Pressurizedsprays, typically aerosols, wherein the active ingredient is dispersedin finely divided form as a result of vaporization of a low boilingdispersant solvent carrier, such as the Freons, may also be used.

The phytotoxic compositions of this invention are applied to the plantsin the conventional manner. Thus, the dust and liquid compositions canbe applied to the plant by the use of power-dusters, boom and handsprayers and spray dusters. The compositions can also be applied fromairplanes as a dust or a spray because they are effective in very lowdosages. In order to modify or control growth of germinating seeds oremerging seedlings, as a typical example, the dust and liquidcompositions are applied to the soil according to conventional methodsand are distributed in the soil to a depth of at least 1/2 inch belowthe soil surface. It is not necessary that the phytotoxic compositionsbe admixed with the soil particles since these compositions can also beapplied merely by spraying or sprinkling the surface of the soil. Thephytotoxic compositions of this invention can also be applied byaddition to irrigation water supplied to the field to be treated. Thismethod of application permits the penetration of the compositions intothe soil as the water is absorbed therein. Dust compositions, granularcompositions or liquid formulations applied to the surface of the soilcan be distributed below the surface of the soil by conventional meanssuch as discing, dragging or mixing operations.

The herbicide can also be applied in the crop furrow or it can beapplied by injection along-side the crop and furrow in rows spacedseveral inches from the seed.

What is claimed is:
 1. A method of selectively controlling undesirablevegetation in sugarbeets comprising applying an herbicidally effectiveamount of S-n-butyl-N,N-diisopropylthiocarbamate.
 2. A method ofselectively controlling undesirable vegetation in carrots comprisingapplying an herbicidally effective amount ofS-n-butyl-N,N-diisopropylthiocarbamate.
 3. A method of selectivelycontrolling undesirable vegetation in cabbage comprising applying anherbicidally effective amount of S-n-butyl-N,N-diisopropylthiocarbamate.